This invention relates to a compressor for a refrigeration system and more particularly to a compressor oil lubrication system wherein oil is slung outwardly from the compressor crankshaft and is deflected upwardly onto the top wall of the compressor shell by means of a counterbore in the outboard bearing so that heat energy is transferred from the compressor oil to the compressor housing.
In hermetic compressors of the type herein described it is desirable to have the compressor operate at lower temperatures so that the compressor operates most efficiently. Lubricating oil is therefore used to both lubricate the moving parts of the compressor and to cool the compressor in order to prevent overheating thereof. Heat transferred to the lubricating oil must be transferred from the oil out of the compressor. A conventional way of transferring the heat from the oil out of the compressor is to spray the oil onto the wall of the compressor housing whereby the housing absorbs the heat from the oil and the heat can then be transferred from the housing to the outside of the compressor by convection to the ambient air surrounding the compressor.
Conventional compressors in general comprise an electric motor and a crankshaft which is rotatably driven by the motor. An oil sump is generally located in the bottom portion of the housing and oil is drawn up therefrom by a crankshaft operated pump and is then conducted through a bore in the crankshaft to radial crankshaft passages to areas in need of lubrication. Excess oil travels further upwardly through the crankshaft bore and is then sprayed outwardly from the crankshaft at an upper portion thereof, and onto the housing to be cooled thereby. The oil runs down the walls of the housing and returns to the oil sump.
Many prior art arrangements have been provided for dispersing the oil from the crankshaft to the housing. In one such arrangement, disclosed in U.S. Pat. No. 3,451,615, an axially directed port and a radially directed port are provided for discharging oil from the crankshaft bore. These two ports are arranged so that centrifugal force discharges oil from the axial bore through the radial port at low crankshaft speeds and through both ports at higher crankshaft speeds. By providing a special notch located in the side of the shaft at the end of the radial bore, the oil is dispersed onto the wall of the upper housing. One problem with this arrangement is that often not all the oil is sprayed onto the housing. A portion of the oil is sprayed onto the shock loop of the discharge refrigerant tube whereby heat which is normally carried out of the compressor by the discharged refrigerant is transferred to the oil instead, and is therefore retained in the compressor. The result of this arrangement is an increase in the operating temperature of the compressor which adversely affects the compressor's efficiency.
In another prior art arrangement disclosed in U.S. Pat. No. 2,628,016 the crankshaft bore extends all the way through the crankshaft. A tube is secured into the upper portion of the bore. The tube is bent at an angle so that oil pumped upwardly through the crankshaft and exiting through the bore and the tube will be sprayed outwardly onto the wall of the compressor housing. While in this arrangement the bent tube can be arranged so that its upper end will extend above the shock loop tube of the compressor, this structure has not been satisfactory since the speed of the compressor varies with its loading. Thus, the speed with which the bent tube which is secured to the upper end of the crankshaft rotates will vary depending upon the compressor speed. The spray pattern of this dispersion arrangement varies with compressor speed and is therefore nonuniform thereby increasing the likelihood that not all the sprayed oil will reach the housing wall. An additional disadvantage of this arrangement is that the bent tube needs to be press fitted into the compressor crankshaft which adds labor and materials cost. In this arrangement it is also possible that the bent tube may work loose thereby causing early failure of the compressor. It is, therefore, desired to provide an arrangement eliminating the need for a special oil dispersion tube.
In yet another prior art arrangement disclosed in U.S. Pat. No. 2,504,528, the top portion of the compressor shell has been deformed so that it is in close proximity to the top of the crankshaft. Oil which is flung out of the bore in the top portion of the crankshaft is deflected by this deformation to run downwardly along the inner wall of the compressor shell. This arrangement also has not been satisfactory because oil sprayed from the top portion of the crankshaft bore is generally flung radially outwardly and does not have sufficient upward velocity to reach the top of the housing. Therefore, only a portion of the oil exiting from the top bore in this compressor will be deposited on the housing to be cooled thereby. It is therefore desired that substantially all the oil sprayed from the top portion of the crankshaft will be flung outwardly onto the housing to be cooled thereby.
In still other prior art arrangements the compressor bore angles radially outwardly at the top end of the compressor crankshaft, in order to impart additional centrifugal velocity to the oil as it is pumped upwardly through the bore of the compressor crankshaft. In these arrangements, insufficient upward velocity is imparted to the oil so that the centrifugal force acting on the oil will cause it to be flung generally radially outwardly of the compressor crankshaft rather than upwardly and onto the housing whereby only a portion of the oil will reach the housing. The remaining oil will be slung onto the working parts of the compressor so that heat is picked up by the oil and the compressor operating temperature will remain higher than is desirable. It is therefore desired that substantially all the oil slung outwardly from the crankshaft bore will be slung directly onto the wall of the compressor housing to be cooled thereby.